PROJECT SUMMARY Suicide is a leading cause of death among youth and recent reports have detected increases in rates. To date, researchers are not able to reliably predict who is most at-risk for suicide, nor do they know when individuals are at most imminent risk. Much of the prior research has focused on distal predictors of suicide ideation (SI) and self-injurious behaviors (SIB; SI/SIB), in other words relations among demographic or diagnostic information present in the years before someone is most at risk. This information may help researchers identify individuals most likely to be at-risk, but is not helpful in identifying when risk is most imminent. Additionally, much of the research has relied on retrospective recall methods, or asking people about their SI/SIB history months and years after someone experienced SI or engaged in SIB. These methods are likely to lead to inaccurate reports of SI/SIB and factors that may have led to them. This study aims to employ ecological momentary assessment (EMA), or questionnaires administered over smart-phones, to understand high-risk for suicide individuals' emotions, coping behaviors, and impulsivity in the moments leading up to SI/SIB among youth ages 16-20. Participants will answer questions daily, 5 times per day, over the course of 14 days aimed at understanding their thoughts and feelings, in addition to the coping strategies they use to regulate affective states. The goal of this research is to more reliably predict not only who, but when, youth are most at-risk for suicide, and to understand more clearly the processes implicated in order to inform and tailor treatments aimed at preventing the occurrence of SI/SIB.